Feasibility of Spirulina platensis Production Using Optimized Beet Filter Cake Extract Medium on Large-Scale Raceway Open Pond

In Egypt, the beet sugar industry produces huge amounts of solid wastes called beet filter cake (BFC), which presents a problem for disposal, polluting the environment. On the other hand, the commercial production of cyanobacterium Spirulina platensis as an alternative protein source is costly. Therefore, this study intended to recycle BFC waste by exploiting it for the economical production of single-cell protein Spirulina platensis on a large scale using an open raceway pond. The cultivation was done in winter using two open ponds of 1000L capacity fitted with a paddle wheel for mixing, which was constructed in the Faculty of Science, Mansoura University, Egypt. One of them was for standard Zarrouk's medium (SZM), and the other was for an optimized beet filter cake extract (BFCE) medium. Environmental conditions, such as temperature and solar radiation, as well as growth parameters, such as optical density, photosynthetic activity, specific growth rate, and dry weight, were monitored every two days. Experimental results showed that the temperature was 19.1- 21°C in SZM and 17.8- 21°C in the optimized BFCE, and the pH increased during the cultivation period to maximum values of 10.5 and 11.1 in SZM and optimized BFCE, respectively, which maintains alkaline conditions. The maximum dry weight values were 0.47 and 0.57g/ l in SZM and optimized BFCE medium at the end of the cultivation period, and there was no significant difference in the Fv/ Fm values in both media. Furthermore, no significant differences were observed in the protein content in both media, which was 55.11± 0.75 and 52.58± 1.31 in SZM and optimized BFCE medium. The cost of biomass produced from optimized BFCE medium is 2.6 times cheaper than that of Zarrouk's medium. Finally, we concluded that optimized BFCE can be used as a promising, cost-effective medium for the large-scale production of single-cell protein Spirulina platensis.